The present invention relates to acassette for supporting substrates and, in particular, to a cassette for effectively precluding the deflection and vibrations of even large-sized substrates during the loading or unloading thereof with respect to the substrate, and to an elongated rib structure for the cassette.
In handling substrates, such as glass substrates, it is necessary to stow, hold and take out the substrates without allowing them to be placed in contact with each other.
The cassette of this type in common use today is a box-like structure having a pair of opposed side walls each containing grooved side panels so that substrates may be removably inserted into the spaces defined by the grooves in the respective side panels. The geometry of the grooved panel may be varied but all available side panels have basically the same construction; namely, a plurality of parallelly disposed rib-like shelves which project inwardly from thickened parts of a pair of predetermined pitch. A substrate can thus be removably inserted into the space between the adjacent rib-like shelves.
The distance the extending rib-like shelves of grooved side panels project in substrate cassettes available today is generally about 10 mm, and even in the case of a cassette for large-sized glass substrates, the distance of projection of the rib-like shelves is generally about 16 mm or less.
Among known cassettes ofthe above type arethe cassettes described in JP Kokai H2-2195150, JP Kokai H3-133152, JP Kokai H5-147680, JP Kokai H6-247483 and JP Kokai H6-286812, all according to the applications filed by the present applicant.
In JP Kokai H9-36219, one of the present applicants proposes a cassette having grooved side panels equipped with rib-like shelves extending over a markedly increased distance; more particularly, a cassette such that the distance of projection of the shelves of its side panels is {fraction (1/10)} to xc2xc of the effective width of the cassette. This published patent application not only proposes such prolongation of rib-like shelves of grooved side panels but also proposes an embodiment in which additional elongated ribs extend from the receiving frame (stopper) in the innermost part of the cassette.
Glass substrates in general use are from 0.7 mm to 1.1 mm in thickness, and substrates with athickness of 0.5 are also coming into popular use. Moreover, substrates as thin as 0.4 mm or 0.3 mm have also come into use recently. Glass substrates are available in various sizes and, while substrates measuring 360 mm to 400 mm in width had formerly constituted a large majority, recently substrates ofmore than 500 mm wide to about 800 mm wide, and even those as wide as about 1000 mm or more have come into use. (Incidently, the length (depth) of the glass substrate is generally equal to the width thereof, or greater.)
Even though glass substrates have excellent rigidity, deflection of a large-sized substrate during loading/unloading of a cassette therewith cannot be disregarded. According to an article at pages 69 to 71 in Monthly LCD Intelligence, 1997.5, the gravitational deflections of glass substrates varying in size and thickness are as shown in Table 1.
As deflection progresses, the smooth insertion and take-out of cassettes are hindered unless the shelf-to-shelf pitch for each stage is increased, but if the pitch is increased, the number of glass substrates which can be accommodated per cassette will be inevitably decreased. If the number of glass substrates to be cassetted is to be kept up to the same numbers as previously, it is necessary to manufacture larger cassettes. Moreover, if a substantial deflection takes place, damage to the glass substrate during cassetting will become a problem which cannot be disregarded.
Compared with earlier cassettes, the long-ribbed cassette described in JP Kokai H9-36219 referred to above represents a marked improvement in the prevention of substrate deflection. However, since the rib-like shelves are made ofresin and are increased in length, the free ends of the shelves are slightly deflected downward when they are loaded with the substrate and the resultant vibration, once produced, is not readily attenuated so that the quality of the substrate tends to be adversely affected in various ways.
In the above state of the art, the object of the present invention is to provide a substrate cassette and an elongated rib for use in the cassette which reflects improvements in the above long-rib system described in JP Kokai H9-36219 and is adapted to effectively prevent said deflection and vibrations even when the cassette is loaded with large-sized substrates.
Accordingly, the elongated-rib structure for a cassette according to the present invention is an elongated rib 3 to be installed as projecting inwardly of a box-shaped skeletal cassette frame 1 from a pair of side panels 2, 2 disposed at two opposed sides of said frame 1 for supporting a substrate, said elongated rib 3 being a three-member structure including:
a base resin body 31,
an elongatedbar-like intermediate resinbody 33 disposedtoprojectfrom the forward end of said base resin body 31, and
a terminal resin body 34 provided at the forward end of said intermediate resin body 33.
In the preferred embodiment, a linear reinforcing member 32 is inserted from the base resin body 31 to the intermediate body 33 or from the base resin body 31 through the intermediate resin body 33 to the terminal resin body 34.
The present invention is further directed to a substrate cassette comprising a box-shaped skeletal frame 1 and side panels 2, 2 disposed at a pair of opposite sides of said box-shaped skeletal frame 1,
a plurality of elongated ribs 3 extending inwardly of said frame 1 from said side panels 2, 2 for supporting substrates B, each of said elongated ribs 3 comprising a three-member structure comprising:
a base resin body 31,
an elongatedbar-like intermediate resin body 33 disposedto project from the forward end of said base body 31, and
a terminal resin body 34 provided at the forward end of said intermediate resin body 33.
In this embodiment, too, itis preferred that alinear reinforcing member 32 is inserted from the base resin body 31 to the intermediate resin body 33 or from the base resin body 31 through the intermediate resin body 33 to the terminal resin body 34.